The function of kidneys, which are glandular organs located in the upper abdominal cavity of vertebrates, is to filter blood and remove waste products. Specifically, kidneys separate water and waste products of metabolism from blood and excrete them as urine through the bladder. Chronic renal failure is a disease of the kidney in which the kidney function breaks down and is no longer able to filter blood and remove waste substances. Should certain toxic waste substances not be removed from the blood, the toxic substances may increase to lethal concentrations within the body.
Hemodialysis is a life-sustaining treatment for patients who have renal failure. Hemodialysis is a process whereby the patient's blood is filtered and toxins are removed using an extracorporeal dialysis machine. For hemodialysis to be effective, large volumes of blood must be removed rapidly from the patient's body, passed through the dialysis machine, and returned to the patient. A number of operations have been developed to provide access to the circulation system of a patient such that patients may be connected to the dialysis machine.
For example, the most commonly performed hemodialysis access operation is a subcutaneous placement of an arteriovenous graft, which is made from a biocompatible tube. The biocompatible tube can be made of, for instance, a fluoropolymer such as polytetrafluoroethylene. One end of the tube is connected to an artery while the other end is connected to a vein. The arteriovenous graft is typically placed either in the leg or arm of a patient.
Blood flows from the artery, through the graft and into the vein. To connect the patient to a dialysis machine, two large hypodermic needles are inserted through the skin and into the graft. Blood is removed from the patient through one needle, circulated through the dialysis machine, and returned to the patient through the second needle. Typically, patients undergo hemodialysis approximately four hours a day, three days a week.
Various problems, however, have been experienced with the use of an arteriovenous graft. For example, arterial steal occurs when excessive blood flow through the arteriovenous graft “steals” blood from the distal arterial bed. Arterial steal can prevent the proper supply of blood from reaching the extremity of a patient.
Various other complications can also occur. For instance, the blood flowing through the arteriovenous graft can often reach turbulent flow rates. This stream of fast moving blood then exits the arteriovenous graft and contacts the vein connected to the graft. This collision between the flow of blood and the vein may cause the development of myointimal hyperplasia which leads to the thickening of the vein walls and a narrowing of the vessel. As the vein narrows, flow through the arteriovenous graft decreases and blood within the graft may ultimately clot.
The cessation of blood flow through the graft caused by clot formation is known as graft thrombosis. Numerous techniques and medications have been studied in attempts to block the development of the scar tissue. Graft thrombosis, however, continues to remain a reoccurring complication associated with the use of arteriovenous grafts.
In view of the above drawbacks, a need currently exists in the art for an arteriovenous graft that can prevent and minimize arterial steal and graft thrombosis. A process for using an arteriovenous graft in minimizing arterial steal and graft thrombosis is also needed.